Metallurgical process



United States Patent 3,310,393 METALLURGICAL PROCESS Leonard L. Cogen,Newark, N.J., assiguor to Union Carbide Corporation, a corporation ofNew York No Drawing. Filed Aug. 5, 1963, Ser. No. 300,102

1 Claim. or. 75-60) This invention relates to an improved metallurgicalmethod for use when introducing gases, liquids or solids intometallurgical furnaces, vessels and the like.

The invention is particularly directed to the use of an improvedmaterial for forming metallurgical lances and blast furnace tuyeres.

Metallurgical lances are now commonplace in the production of steel.These lances are currently used primarily for blowing gaseous oxidantsinto a molten metal bath within open hearth furnaces and basic oxygenprocess vessels. An example for such a lance is disclosed andillustrated in U.S. Patent 3,020,035 issued Feb. 6, 1962 to G. W. Hindset al. As disclosed therein, it has been necessary to provide internalwater cooling systems to better enable the equipment to withstand thesevere chemical attack of heated iron and slag particles which arecontinuously thrown against the equipment while it is operating in ahighly oxidizing, high temperature atmosphere. Notwithstanding variousbasic nozzle configurations utilized in addition to other designchanges, and water cooling, the life of this equipment is relativelyshort.

It has been the general practice within the industry to fabricate thismetallurgical injection equipment of oxygen-free copper. Usually, onlythe nozzle end of the apparatus which is actually exposed to the mostintense reaction areas within the furnace is fabricated of copper, withthe remaining parts formed of steel. The copper nozzle is subjected tosevere attack from the splashing and abrasion thereon of heatedparticles of iron and slag. The rapid wearing away of the copper nozzleis believed to be caused by extremely hot particles of iron striking andadhering to the nozzle surfaces. These iron particles are then burned onthe copper surface by the surrounding highly oxidizing atmosphere.

This iron oxidation reaction liberates intense localized heat which issuflicient to cause a scarfing or wearing away of the copper surface.The problem is thus believed to be characterized as a high temperatureoxidation of the copper whereby the copper actually diffuses to thesurface of the nozzle to continuously form a film of copper oxide, untilthe nozzle progressively wears away.

While a blast furnace tuyere is not subjected to the same hightemperature, highly oxidizing atmosphere that a metallurgical lanceencounters, still the problem of wear is similar whenever oxidants suchas air, air enriched with oxygen, of pure oxygen, are injected throughthe tuyeres into the furnace. While the overall atmosphere within theblast furnace is reducing, the immediate localized area adjacent thetuyere discharge nozzle end will have an oxidizing affect on the tuyerenozzle whenever the oxidant is being blown into the furnace.

It is an object of this invention to provide an improved method ofrefining a molten steel bath when reacting oxygen therewith.

Another object is to provide a satisfactory material for use infabricating at least the exposed nozzle portion of metallurgicalapparatus for injecting gases, liquids or solids into furnaces operatingwith a high temperature, highly oxidizing atmosphere.

Another object is to provide a suitable and satisfactory material foruse in forming at least the discharge nozzle portion of a metallurgicallance, and which will withstand prolonged operation in a hightemperature, highly oxidizing atmosphere, when exposed to direct contactwith hot iron particles. 1 i

A further object is to provide a material which is suitable andsatisfactory for use in forming at least the nozzle discharge end of ablast furnace tuyere and which will withstand prolonged operation whenintroducing oxidants into a high temperature blast furnace and whenexposed during such operation to direct contact with heated ironparticles.

The first object is attained according to the present invention, in amethod of refining a molten steel bath by reacting oxygen therewith, byblowing the oxygen into the bath through a lance having at least anozzle discharge end composed of an alloy consisting essentially of0.05% to 0.2% zirconium by weight and the remainder of initiallyoxygen-free copper.

The remaining objects are attained according to the invention by the useof a material consisting essentially of 0.05 to 0.2% zirconium by weightand the remainder initially oxygen-free copper.

This alloy may be prepared according to conventional alloying proceduresby adding between 0.05 and 0.2% zirconium metal to an initiallyoxygen-free copper such as, for example, OFHC brand copper.

If other metals are present they should not be subversive to thecharacteristics of the copper-zirconium alloy.

This copper-zirconium alloy material has been found to possess anextremely high resistance to chemical attack by the iron-oxygen scarfingreaction occurring at its surface, in addition to possessing a highthermal conductivity at elevated temperatures when compared to thethermal conductivity of copper at such temperatures. It is believed thatthe zirconium diffuses to the surface of the copper whereupon it forms azirconia-rich surface layer which holds tenaciously to the surface. Thislayer, it is believed, acts to greatly retard the outward diffusion ofthe copper.

It is to be noted that merely plating a copper surface with zirconia isineffective as it is difficult to form a bonding which will provide thesame long lasting protective layer.

Many alternative materials have been tried, without success, in aneffort to extend the operational life of metallurgical lances. The useof highly oxidation resistant materials such as stainless steel andMonel, for example, were ineffective since such materials did not havesuificiently high thermal conductivity at elevated temperatures. The useof oxygen-free copper, on the other hand, did not provide sufficientresistance to the high temperature oxidizing chemical attack by the ironparticles, although it did have a high thermal conductivity at elevatedtemperatures.

The practicability of using the copper-zirconium alloy for fabricating ametallurgical lance was demonstrated by forming the nozzle discharge endof a conventional lance of this alloy. Another nozzle discharge end ofidentical design was formed of oxygen-free copper. Both lances wereinserted in open hearth furnaces operating under the same commercialconditions. The lance with the copper nozzle discharge end-failed after100 hours of operation, whereas the lance with the copper-zirconiumnozzle discharge end did not fail until it had been operating 500 hours.In two similar tests the copper-zirconium nozzles lasted 489 and 501 /2hours, respectively, while the copper nozzles of identical design lastedbut /2 and 113 hours, respectively.

What is claimed is:

In a method of refining a molten steel bath by reacting oxygentherewith, the step of blowing a stream of oxygen through a lance havinga nozzle discharge end References Cited by the Examiner UNITED STATESPATENTS 2/1958 McFeaters 266-34 4 V Bieniosek et al 266-41 Vogt 756OSaarivirta et a1 75153 Hudson 26634 BENJAMIN HENKIN, Primary Examiner.

